What Type of Corn Gluten Do You Use for Weed Prevention?

Corn gluten meal is a natural herbicide that will prevent most weed seeds from germinating.

Controlling weeds like dandelions, crabgrass and chickweed that readily produce seeds can seem like an endless battle for any gardener. The seeds sprout so easily and grow so fast that it feels like you can never gain the upper hand. Corn gluten meal (CGM), however, is an effective and natural means of managing weeds by preventing seed germination. A byproduct of corn milling, CGM is a pre-emergence herbicide, meaning that it works on seeds in the ground and prevents them from establishing roots. CGM will not discourage existing weeds, but it will keep new generations from growing.

Advantages

Available in powder or pellet form, CGM is easy to apply and is safe for humans and animals; so safe, in fact, that it is used to feed livestock. It's also safe for ornamental and edible plants that are already established. Additionally, there's a bonus -- CGM contains approximately 10 percent nitrogen by weight, so as it decomposes, it feeds your plants.

Disadvantages

There isn't much of a downside to using CGM, but there are a few issues to be aware of. While water is needed to activate CGM, too much water can render it ineffective, so excessive rainfall can negate your weed control efforts. In addition, because CGM inhibits germination of most seeds, it will also prevent any plants that you want to reseed from doing so. It should be noted as well that the nitrogen in CGM can benefit already existing weeds, making them hardier and more difficult to eradicate.

Applying to Lawns

To control new weed growth in lawns, two applications per year are recommended, first in April or May and again in August. Broadcast evenly over the area at a rate of 20 pounds per 1,000 square feet and watered in lightly to activate it, CGM will remain active for five to six weeks each time. Results will not be immediately apparent, but if used consistently, CGM will noticeably reduce the weed population.

Applying in Flower and Vegetable Beds

CGM can be used just as effectively around ornamentals and edibles as on lawns. Allow new flower or vegetable seedlings and transplants to become established before applying the CGM. Lightly cultivating the CGM into the topsoil around the plants can increase its effectiveness, as compared to only spreading it on top the soil.

About the Author

Claire Splan is a writer and editor living in the San Francisco Bay Area. She is the author of "California Month-by-Month Gardening" and "California Fruit and Vegetable Gardening" (both published by Cool Springs Press) and blogs about gardening at An Alameda Garden (http://www.alamedagarden.blogspot.com).